African Americans are at high risk of cardiovascular disease (CVD) but generally have limited success in weight loss and lifestyle change programs. We propose to examine the role of social support, particularly from family members and friends, in facilitating weight loss and related dietary and physical activity changes in African Americans. Men and women will be recruited from an urban, university health system and the surrounding community. Those eligible as "index" participants will be African Americans ages 35 to 70 years (n=128) with a body mass index (BMI) of 27 to 50 kg/m2 and at least one obesity-related co-morbidity or clinical CVD risk factor. Index participants will be encouraged but not required to name 1 or 2 family member or friend co-participants. Co-participants will be eligible if they are aged 16 to 70 years and have a BMI in the same range as index participants by adult or adolescent BMI criteria. All index participants will receive the same group, behavioral counseling program supplemented with individual counseling. Contact will be weekly, then biweekly, then monthly over 24 months. Index participants who name co-participants will be randomly assigned in a 1:1 ratio to high (Group A, direct involvement of family members and friends) or low (Group B, indirect involvement of family members and friends) social support conditions. In Group A, both index and co-participants will be included in all counseling sessions. In Group B, co-participants will not be included in group counseling sessions but will be given self-help materials and invited to accompany index participants to individual counseling sessions. Index participants who do not identify co-participants (n=64) will be randomly assigned in a 1:1 ratio to high (Group C, assigned to teams with other index participants) or low (Group D, not so assigned) social support. Data on weight, clinical CVD risk, diet, physical activity, psychosocial factors and social support will be collected from participants and, for most variables, from co-participants at baseline and semiannually. Primary hypotheses are that weight loss from 0 to 12 months, 0 to 24 months, and weight maintenance from 12 to 24 months will be greater in Group A vs. Group B and in Group C vs. Group 0. Secondary analyses will compare the respective treatment and control groups on diet, physical activity, and clinical CVD risk factor changes and will assess predictors of outcomes and cost-effectiveness.